[PATCH 1/1] mm: smaps: split PSS into components

[semenzato@chromium.org]

From: Luigi Semenzato <semenzato@chromium.org>

Report separate components (anon, file, and shmem)
for PSS in smaps and smaps_rollup.

This helps understand and tune the memory manager behavior
in consumer devices, particularly mobile devices.  Many of
them (e.g. chromebooks and Android-based devices) use zram
for anon memory, and perform disk reads for discarded file
pages.  The difference in latency is large (e.g. reading
a single page from SSD is 30 times slower than decompressing
a zram page on one popular device), thus it is useful to know
how much of the PSS is anon vs. file.

This patch also removes a small code duplication in smaps_account,
which would have gotten worse otherwise.

Signed-off-by: Luigi Semenzato <semenzato@chromium.org>
---
 fs/proc/task_mmu.c | 61 ++++++++++++++++++++++++++++------------------
 1 file changed, 37 insertions(+), 24 deletions(-)

diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index 01d4eb0e6bd1..4b586c4d27b0 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -417,17 +417,45 @@ struct mem_size_stats {
 	unsigned long shared_hugetlb;
 	unsigned long private_hugetlb;
 	u64 pss;
+	u64 pss_anon;
+	u64 pss_file;
+	u64 pss_shmem;
 	u64 pss_locked;
 	u64 swap_pss;
 	bool check_shmem_swap;
 };
 
+static void smaps_page_accumulate(struct mem_size_stats *mss,
+		struct page *page, unsigned long size, unsigned long pss,
+		bool dirty, bool locked)
+{
+	mss->pss += pss;
+
+	if (PageAnon(page))
+		mss->pss_anon += pss;
+	else if (PageSwapBacked(page))
+		mss->pss_shmem += pss;
+	else
+		mss->pss_file += pss;
+
+	if (locked)
+		mss->pss_locked += pss;
+	if (dirty || PageDirty(page))
+		mss->shared_dirty += size;
+	else
+		mss->shared_clean += size;
+}
+
 static void smaps_account(struct mem_size_stats *mss, struct page *page,
 		bool compound, bool young, bool dirty, bool locked)
 {
 	int i, nr = compound ? 1 << compound_order(page) : 1;
 	unsigned long size = nr * PAGE_SIZE;
 
+	/*
+	 * First accumulate quantities that depend only on |size| and the type
+	 * of the compound page.
+	 */
 	if (PageAnon(page)) {
 		mss->anonymous += size;
 		if (!PageSwapBacked(page) && !dirty && !PageDirty(page))
@@ -440,42 +468,24 @@ static void smaps_account(struct mem_size_stats *mss, struct page *page,
 		mss->referenced += size;
 
 	/*
+	 * Then accumulate quantities that may depend on sharing, or that may
+	 * differ page-by-page.
+	 *
 	 * page_count(page) == 1 guarantees the page is mapped exactly once.
 	 * If any subpage of the compound page mapped with PTE it would elevate
 	 * page_count().
 	 */
 	if (page_count(page) == 1) {
-		if (dirty || PageDirty(page))
-			mss->private_dirty += size;
-		else
-			mss->private_clean += size;
-		mss->pss += (u64)size << PSS_SHIFT;
-		if (locked)
-			mss->pss_locked += (u64)size << PSS_SHIFT;
+		smaps_page_accumulate(mss, page, size, size, dirty, locked);
 		return;
 	}
-
 	for (i = 0; i < nr; i++, page++) {
 		int mapcount = page_mapcount(page);
 		unsigned long pss = (PAGE_SIZE << PSS_SHIFT);
-
 		if (mapcount >= 2) {
-			if (dirty || PageDirty(page))
-				mss->shared_dirty += PAGE_SIZE;
-			else
-				mss->shared_clean += PAGE_SIZE;
-			mss->pss += pss / mapcount;
-			if (locked)
-				mss->pss_locked += pss / mapcount;
-		} else {
-			if (dirty || PageDirty(page))
-				mss->private_dirty += PAGE_SIZE;
-			else
-				mss->private_clean += PAGE_SIZE;
-			mss->pss += pss;
-			if (locked)
-				mss->pss_locked += pss;
+			pss /= mapcount;
 		}
+		smaps_page_accumulate(mss, page, PAGE_SIZE, pss, dirty, locked);
 	}
 }
 
@@ -758,6 +768,9 @@ static void __show_smap(struct seq_file *m, const struct mem_size_stats *mss)
 {
 	SEQ_PUT_DEC("Rss:            ", mss->resident);
 	SEQ_PUT_DEC(" kB\nPss:            ", mss->pss >> PSS_SHIFT);
+	SEQ_PUT_DEC(" kB\nPss_Anon:       ", mss->pss_anon >> PSS_SHIFT);
+	SEQ_PUT_DEC(" kB\nPss_File:       ", mss->pss_file >> PSS_SHIFT);
+	SEQ_PUT_DEC(" kB\nPss_Shmem:      ", mss->pss_shmem >> PSS_SHIFT);
 	SEQ_PUT_DEC(" kB\nShared_Clean:   ", mss->shared_clean);
 	SEQ_PUT_DEC(" kB\nShared_Dirty:   ", mss->shared_dirty);
 	SEQ_PUT_DEC(" kB\nPrivate_Clean:  ", mss->private_clean);
-- 
2.21.0.1020.gf2820cf01a-goog